| 摘要 |
PURPOSE: To obtain Co-contg. magnetic iron oxide powder excellent in magnetic stability by successively coating the surfaces of acicular iron oxide hydrate particles with hydroxides of Co, Mn and Si and carrying out dehydration by heating, reduction, partial oxidation and heating. CONSTITUTION: The surfaces of acicular iron oxide hydrate particles are successively coated with Co hydroxide, Mn hydroxide and Si hydroxide or Si hydroxide and Al hydroxide. The coated particles are dehydrated by heating and reduced. The resultant magnetite powder is partially oxidized so that the Fe<2+> content is regulated to 13-18wt.% of the amt. of magnetic iron oxide and then the powder is heated at 450-600 deg.C in an inert atmosphere and cooled to 50-90 deg.C at <2 deg.C/min rate to obtain the objective Co-contg. magnetic iron oxide powder especially suitable for a magnetic recording medium for high density recording. The coercive force Hc of this powder increases by <=20Oe after the lapse of three weeks in N2 at room temp. and the Fe<2+> content is retained at >=65% rate after the lapse of three weeks in air at 60 deg.C. |
